Lithium-ion batteries (LIBs) have the highest gravimetric and volumetric energy densities among the commercialized batteries that can provide electric drives for plug-in hybrid (PHEVs) and fully electric vehicles (EVs). All lithium-ion battery cells are built from a positive electrode (cathode) and a negative electrode (anode), electrically isolated by a thin separator and combined with a liquid transporting medium, the electrolyte. Both the anode and the cathode contain active materials into which lithium ions insert and extract. The lithium ions move through an electrolyte from the negative electrode (anode) to the positive electrode (cathode) during discharge, and in reverse, from the positive electrode (cathode) to the negative electrode (anode), during recharge. The anode is typically composed of lithium, dissolved as ions, into a carbon or in some cases metallic lithium. The cathode material is made up from lithium liberating compounds, typically electro-active oxide materials.
Electrode design has been a key aspect in achieving the energy and power density, and life performance required for electric vehicle (EV) batteries. High energy densities can only be realized by increasing the specific energies on both the cathode and the anode. Among the cathode materials, Ni-rich materials such as LiNixMnyCozO2 (NMC: x+y+z=1; e.g., x:y:z=8:1:1 (NMC811) and x:y:z:=6:2:2 (NMC622)) and Li [Ni0.8Co0.15Al0.05]O2 (NCA) in particular are the most promising cathode candidates for EVs among the next-generation of high energy density cells owing to their high capacity, excellent rate capability, and low cost. Despite the advantages, increasing the Ni fraction in the NMC cathodes negatively impacts the lifetime and safety of the battery, particularly when higher cut-off voltages and high electrode packing densities are pursued (See e.g., H. J. Noh, et al., J. Power Sources, 2013, 233, 121). A number of strategies have been explored to increase the stability of the Ni-enriched NMC cathode material by suppressing the parasitic side reactions with the electrolyte. (See e.g., Y. K. Sun, et al., J. Am. Chem. Soc., 2015, 127, 13411; Y. K. Sun, et al., Nat. Mater., 2009, 8, 320; Y. K. Sun, et al., Nat. Mater., 2012, 11, 942; H. J. Noh, et al., Chem. Mater., 2013, 25, 2109; B. B. Lim, et al., Adv. Funct. Mater., 2015, 25(29), 4673). Among the anode materials for LIBs, silicon (Si) exhibits the highest gravimetric capacity (3579 mA h/g when charged to Li15Si4); however, a large volume change during cycling often results in pulverization, electrical contact loss, and constant evolution of the solid-electrolyte interphase (SEI), leading to rapid capacity fading. (See e.g., M. N. Obrovac and L. Christensen, Electrochem. Solid-State Lett., 2004, 7, A93; S. D. Beattie, et al., J. Electrochem. Soc., 2008, 155, A158; H. Wu and Y. Cui, Nano Today, 2012, 7, 414; C. Wang et al., Nat. Chem., 2013, 5, 1042).
Accordingly, it is an object of the present invention to overcome, or at least alleviate, one or more difficulties and deficiencies related to the prior art in developing a rechargeable lithium-ion battery delivering high energy density, excellent safety and cycle life. These and other objects and features of the present invention will be clear from the following disclosure.